Minimally invasive surgery may include various benefits such as reduced post operative discomfort, reduced chance of infection, quicker recovery times, shorter hospital stays, quicker return to full activity, smaller external scars and less internal scarring. Accurate and precise manipulation of surgical tools or instruments is desired during any surgical procedure, but this is particularly true with minimally invasive surgery.
Minimally invasive surgery, such as endoscopic procedures, is typically performed through small incisions limiting the room to maneuver the surgical tools. Although surgeries performed using minimally invasive techniques reduce patient trauma and recovery time, traditional methods of performing minimally invasive surgery also limit surgical dexterity and vision. Minimally invasive surgery is typically performed using long, rigid surgical tools that are inserted through an entry point such as a small incision or a natural orifice. For example, laparoscopy is an endoscopic procedure where surgical tools are inserted into an abdominal cavity. Therefore, the maneuverability of the surgical tools is limited due to the constraints of the entry point.
In approximately the last decade, robotic apparatuses have been applied in surgical settings to augment the surgeon's ability to manipulate surgical tools during minimally invasive surgery. Typically, robotic apparatuses include tools that are inserted into a body cavity through the entry point. Main advantages of robotic apparatuses include precise localization in terms of position and orientation of the surgical tools, reduction of surgeon hand tremor, remotely manipulated operation such as telesurgery, and limitation of risks such as the ability to constrain motion of the surgical tool within “safe regions”. “Safe regions” are the areas of main focus of the surgery.
One of the primary problems with current robotic apparatuses is the voluminous size, causing competition for precious space within the operating room environment. Due to size, these apparatuses may cause unwanted safety issues by interacting with other equipment or personnel in the operating room environment. Size also has an effect on control of the robotic apparatus. Likewise, tactile feedback to enhance user-friendliness of the interface of current robotic apparatuses creates additional mass and inertia in particular parts of the apparatus, such as the robotic arms, thereby limiting effectiveness.
A key feature of most robotic apparatuses is the Remote Center of Motion (“RCM”), which allows the surgical tool to pivot about a fixed point in space usually coincident with the entry point of the tool through the entry point. Although some robotic apparatuses use a passive RCM, a mechanically constrained RCM is often considered safer. Yet some apparatuses use software to create a virtually constrained RCM.
There are a variety of ways to achieve a mechanically constrained RCM such as using a special type of wrist mechanism such as spherical wrist mechanism. For example, all rotation axes of a spherical wrist mechanism consist of revolute joints intersecting at the center of the device. One way to implement this is using parallelogram linkages, although other linkage configurations also exist.
Research has led to robotic apparatuses with spherical wrist mechanisms for specific minimally invasive surgery applications, for example, a Light Endoscope Robot (“LER”) for positioning an endoscopic camera. A disadvantage of the LER, however, is that it only provides three Degrees of Freedom (“DOF”)—two rotations around the entry point and one translation along an axis—due to the configuration of the spherical wrist mechanism. Yet another apparatus, similar to LER, is a force controlled robot known as MC2E with four DOF. Other known apparatuses utilize spherical wrist mechanisms with only two DOF—two rotations around the entry point. These spherical wrist mechanisms include actuators that are directly mounted at the joints, which may add inertial loads adversely affecting performance.
To enhance assimilation of surgical robot apparatuses in the operating room environment, it is desirable to have a light-weight system with a structure smaller than existing apparatuses while maintaining large orientation capabilities and precision for controlling surgical tools during minimally invasive surgery. The present invention satisfies this demand.